Communication System, Mobile Station, And Communication Method

Abstract

A communication system includes a mobile station and a base station. The mobile station calculates estimated TA information based on the position of the mobile station and an amount of propagation path delay. The mobile station determines, based on TA information transmitted from the base station and the estimated TA information, whether the TA information is addressed thereto. The mobile station determines whether to transmit “Message 3 ” to the base station depending on determination results, and transmits “Message 3 ” when the TA information is addressed thereto.

1 . A communication system comprising:
 a base station; and   a mobile station that communicates with the base station, and includes
 a first transmitting unit that transmits a first signal containing a preamble number to the base station, 
 a receiving unit that receives from the base station first timing information indicating a difference between reference time of the base station and time the first signal has arrived at the base station, 
 a calculating unit that calculates second timing information indicating a difference between the reference time of the base station and time the first signal is expected to arrive at the base station, and 
 a second transmitting unit that transmits to the base station any one of the first signal and a second signal containing individual information unique to the mobile station based on the first timing information and the second timing information. 
   
   
   
       2 . The communication system according to  claim 1 , wherein the calculating unit calculates the second timing information based on at least one of a distance between the base station and the mobile station and an amount of delay of a radio wave transmitted or received between the base station and the mobile station. 
   
   
       3 . The communication system according to  claim 1 , wherein the second transmitting unit transmits to the base station any one of the first signal and the second signal containing the individual information unique to the mobile station based further on at least one of moving velocity of the mobile station and received signal power. 
   
   
       4 . The communication system according to  claim 1 , wherein
 the first transmitting unit sets one of a plurality of pre-arranged preamble numbers to the first signal and transmits the first signal to the base station, and   the second transmitting unit changes, when transmitting the first signal to the base station, the preamble number set to the first signal.   
   
   
       5 . The communication system according to  claim 1 , wherein the second transmitting unit changes, when transmitting the first signal to the base station, time to transmit the first signal based on the first timing information. 
   
   
       6 . The communication system according to  claim 1 , wherein the second transmitting unit changes, when transmitting the first signal to the base station, transmission power of the first signal. 
   
   
       7 . A mobile station that communicates with a base station comprising:
 a first transmitting unit that transmits a first signal containing a preamble number to the base station;   a receiving unit that receives from the base station first timing information indicating a difference between reference time of the base station and time the first signal has arrived at the base station;   a calculating unit that calculates second timing information indicating a difference between the reference time of the base station and time the first signal is expected to arrive at the base station; and   a second transmitting unit that transmits to the base station any one of the first signal and a second signal containing individual information unique to the mobile station based on the first timing information and the second timing information.   
   
   
       8 . The mobile station according to  claim 7 , wherein the calculating unit calculates the second timing information based on at least one of a distance between the base station and the mobile station and an amount of delay of a radio wave transmitted or received between the base station and the mobile station. 
   
   
       9 . The mobile station according to  claim 7 , wherein the calculating unit corrects the second timing information based on at least one of moving velocity of the mobile station and received signal power. 
   
   
       10 . The communication system according to  claim 7 , wherein
 the first transmitting unit sets one of a plurality of pre-arranged preamble numbers to the first signal and transmits the first signal to the base station, and   the second transmitting unit changes, when transmitting the first signal to the base station, the preamble number set to the first signal.   
   
   
       11 . The communication system according to  claim 7 , wherein the second transmitting unit changes, when transmitting the first signal to the base station, time to transmit the first signal based on the first timing information. 
   
   
       12 . The communication system according to  claim 7 , wherein the second transmitting unit changes, when transmitting the first signal to the base station, transmission power of the first signal. 
   
   
       13 . A communication method applied to a mobile station that communicates with a base station, the communication method comprising:
 transmitting a first signal containing a preamble number to the base station;   receiving from the base station first timing information indicating a difference between reference time of the base station and time the first signal has arrived at the base station;   calculating second timing information indicating a difference between the reference time of the base station and time the first signal is expected to arrive at the base station; and   transmitting to the base station any one of the first signal and a second signal containing individual information unique to the mobile station based on the first timing information and the second timing information.